Optical device and display device

Abstract

To provide an optical device capable of improving reduction performance of speckle noise.SOLUTION: The optical device comprises: a laser source; a first integrator optical system transmitting a laser beam emitted from the laser source; a second integrator optical system transmitting the laser beam emitted from the first integrator optical system; and a retardation plate arranged between the laser source and the second integrator optical system and transmitting part of the laser beam to rotate polarization of the transmitted laser beam by 90 degrees.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to an optical device and a display device. [Background technology]

[0002] 2. Description of the Related Art Optical devices that emit laser light and are mounted on display devices that display images using laser light are known.

[0003] For example, Patent Document 1 discloses a light source device that rotates the polarization of laser light output from a laser light source by 90 degrees using a half-wave plate in order to reduce speckle noise caused by scattering of the laser light. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2011-242537 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, the device described in Patent Document 1 uses only the polarized light of the laser light from the laser light source, so there is room for improvement in terms of speckle noise reduction performance.

[0006] An object of the embodiment of the present disclosure is to provide an optical device capable of improving the performance of reducing speckle noise. [Means for solving the problem]

[0007] An optical device according to one embodiment of the present disclosure includes a laser light source, a first integrator optical system that transmits laser light emitted from the laser light source, a second integrator optical system that transmits the laser light emitted from the first integrator optical system, and a retardation plate disposed between the laser light source and the second integrator optical system, which transmits a portion of the laser light, thereby rotating the polarization of the transmitted laser light by 90 degrees. Effect of the Invention

[0008] According to an embodiment of the present disclosure, an optical device capable of improving the performance of reducing speckle noise can be provided. [Brief description of the drawings]

[0009] [Figure 1] 1 is a schematic cross-sectional view of an optical device according to a first embodiment. [Diagram 2] 2 is a schematic plan view showing a first example of the positional relationship between a laser light source and a retardation plate in the optical device according to the first embodiment. FIG. [Diagram 3] 2 is a schematic perspective view of a first fly-eye lens included in a first integrator optical system of the optical device according to the first embodiment. FIG. [Figure 4] 3 is a schematic perspective view of a third fly-eye lens included in a second integrator optical system of the optical device according to the first embodiment. FIG. [Diagram 5] 4 is a schematic cross-sectional view of a second illumination optical system, illustrating how two orthogonal polarized beams are incident on an irradiation surface in the optical device according to the first embodiment. FIG. [Figure 6] 5 is a schematic plan view showing a second example of the positional relationship between the laser light source and the retardation plate in the optical device according to the first embodiment. FIG. [Figure 7] FIG. 11 is a schematic cross-sectional view of an optical device according to a second embodiment. [Figure 8] 11 is a schematic cross-sectional view of a second illumination optical system, illustrating how two orthogonal polarized beams are incident on an irradiation surface in an optical device according to a second embodiment. FIG. [Figure 9]11 is a schematic cross-sectional view showing a first example of the configuration around a laser light source in an optical device according to a third embodiment. FIG. [Figure 10] 13 is a schematic cross-sectional view showing a second example of the configuration around a laser light source in an optical device according to a third embodiment. FIG. [Figure 11] 13 is a schematic plan view showing a first example of the positional relationship between combined light and a retardation plate in an optical device according to a third embodiment. FIG. [Figure 12] 13 is a schematic plan view showing a second example of the positional relationship between the combined light and the retardation plate in the optical device according to the third embodiment. FIG. [Figure 13] FIG. 13 is a schematic cross-sectional view of an optical device according to a fourth embodiment. [Figure 14] FIG. 13 is a schematic cross-sectional view of a display device according to a fifth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] An optical device and a display device according to an embodiment of the present disclosure will be described in detail with reference to the drawings. However, the following embodiments are merely illustrative of an optical device and a display device for embodying the technical idea of ​​the present disclosure, and are not limited to the following. Furthermore, unless otherwise specified, the dimensions, materials, shapes, and relative arrangements of the components described in the embodiments are merely illustrative examples, and are not intended to limit the scope of the present disclosure to those alone. Note that the size, positional relationship, etc. of the components shown in each drawing may be exaggerated to clarify the explanation. In addition, in the following explanation, the same names and symbols indicate the same or similar components, and detailed explanations will be omitted as appropriate. An end view showing only a cut surface may be used as a cross-sectional view.

[0011] In each drawing, a Cartesian coordinate system having an X-axis, a Y-axis, and a Z-axis is used to represent directions. The X-axis, the Y-axis, and the Z-axis are mutually perpendicular. The side toward which the arrow points in the X direction along the X-axis is indicated as the +X side, and the side opposite the +X side is indicated as the -X side. The side toward which the arrow points in the Y direction along the Y-axis is indicated as the +Y side, and the side opposite the +Y side is indicated as the -Y side. The side toward which the arrow points in the Z direction along the Z-axis is indicated as the +Z side, and the side opposite the +Z side is indicated as the -Z side.

[0012] The Z axis is along the normal of the retardation plate of the optical device according to the embodiment. The optical device according to the embodiment emits laser light to the +Z side. In the terminology of the embodiment, planar view refers to viewing an object from the +Z side or the -Z side. A plan view of an object means a view of the object in a planar view. However, these do not limit the orientation of the optical device and display device according to the embodiment when used, and the orientation of the optical device and display device according to the embodiment is arbitrary.

[0013] In the following embodiments, along the X-axis, Y-axis, and Z-axis includes the object having a tilt within ±10 degrees relative to these axes. In the embodiments, each of the perpendicular and perpendicular directions may have an error within ±10 degrees relative to 90 degrees. Also, a rotation of 90 degrees may have an error within ±10 degrees. Furthermore, half of the object may have an error within ±10% of the object.

[0014] In addition, in this specification or claims, when there are multiple elements of a certain type and each element is to be expressed with a distinction, the elements may be distinguished by adding "first," "second," etc. to the beginning of the element. In addition, the objects to be distinguished may differ between this specification and the claims. Therefore, even if the claims describe an element with the same notation as this specification, the object identified by this element may not match between this specification and the claims.

[0015] [First embodiment] An optical device according to the first embodiment will be described with reference to FIGS. 1 to 5. FIG. 1 is a schematic cross-sectional view showing an example of the optical device 100 according to the first embodiment. FIG. 1 shows a cross-section of the optical device 100 cut along a virtual plane (e.g., a YZ plane) including the optical axis A of the optical device 100. The optical axis A of the optical device 100 is an axis passing through the center of the first integrator optical system 2 of the optical device 100. FIG. 2 is a schematic plan view showing a first example of the positional relationship between the laser light source 1 and the retardation plate 4 in the optical device 100. FIG. 3 is a schematic perspective view of the first fly-eye lens 21 of the first integrator optical system 2 of the optical device 100. FIG. 4 is a schematic perspective view of the third fly-eye lens 31 of the second integrator optical system 3 of the optical device 100. FIG. 5 is a schematic cross-sectional view of the second illumination optical system 30 showing how two orthogonal polarized lights are incident on the irradiation surface S in the optical device 100. FIG. 5 shows a cross section of the optical device 100 cut along a virtual plane (eg, a YZ plane) including the optical axis A of the optical device 100.

[0016] The optical device 100 includes a laser light source 1, a first integrator optical system 2 that transmits the laser light L emitted from the laser light source 1, and a second integrator optical system 3 that transmits the laser light L emitted from the first integrator optical system 2. The optical device 100 also includes a retardation plate 4 that is disposed between the laser light source 1 and the second integrator optical system 3 and transmits a part of the laser light L to rotate the polarization of the transmitted laser light L by 90 degrees. In the example shown in FIG. 1, the optical device 100 also includes a first lens 5, a second lens 6, a third lens 7, and a fourth lens 8. The first integrator optical system 2, the first lens 5, and the second lens 6 constitute a first illumination optical system 20. The second integrator optical system 3, the third lens 7, and the fourth lens 8 constitute a second illumination optical system 30. The second integrator optical system 3 can include a third fly-eye lens 31.

[0017] 1, the laser light source 1 includes a semiconductor laser element 11, a substrate 13 including a recess on the +Z side surface, a lid member 12, and an optical member 16. The semiconductor laser element 11 is disposed in the recess of the substrate 13. The recess of the substrate 13 is sealed by the lid member 12, and the optical member 16 is disposed on the +Z side surface of the lid member 12. The semiconductor laser element 11 can emit laser light L in response to a current supplied via the substrate 13, etc.

[0018] As shown in Fig. 2, the laser light source 1 includes four first semiconductor laser elements 11R that emit red laser light, two second semiconductor laser elements 11G that emit green laser light, and two third semiconductor laser elements 11B that emit blue laser light. The semiconductor laser element 11 in Fig. 1 includes the four first semiconductor laser elements 11R, two second semiconductor laser elements 11G, and two third semiconductor laser elements 11B. The laser light L in Fig. 1 includes laser light emitted from each of the four first semiconductor laser elements 11R, two second semiconductor laser elements 11G, and two third semiconductor laser elements 11B.

[0019] 1 and 2, the laser light source 1 emits linearly polarized laser light L from the semiconductor laser element 11. The laser light L is, for example, P-polarized light. The retardation plate 4 transmits a portion of the laser light L emitted from the semiconductor laser element 11, and emits S-polarized light whose polarization direction is rotated 90 degrees with respect to the P-polarized light of the transmitted laser light L. Of the laser light L, the P-polarized light that was not transmitted by the retardation plate 4 and the S-polarized light that was transmitted by the retardation plate 4 are incident on the first integrator optical system 2.

[0020] The retardation plate 4 is, for example, a half-wave plate. In the example shown in FIG. 2, the shape of the retardation plate 4 in plan view is a substantially rectangular shape with the longer side in the horizontal direction (for example, the X direction) perpendicular to the vertical direction. However, the shape of the retardation plate 4 in plan view may be substantially circular, substantially elliptical, substantially polygonal, or the like. The normal line of the retardation plate 4 substantially coincides with the optical axis A, for example. The half-wave plate may be made of a crystal having birefringence, or may be made including a resin having birefringence. The retardation plate 4 is disposed such that the optical axis of the half-wave plate is inclined by 45 degrees with respect to the polarization direction of the laser light L, which is linearly polarized light. This allows the retardation plate 4 to rotate the polarization of the laser light L that is transmitted through the retardation plate 4 by 90 degrees.

[0021] In the example shown in Fig. 1, each of the first integrator optical system 2 and the second integrator optical system 3 generates a light flux with uniform illuminance from the laser light L emitted from the laser light source 1. The laser light L from the laser light source 1 passes through the first integrator optical system 2, and then passes through a first lens 5 and a second lens 6 to be incident on the second integrator optical system 3. The laser light L that has passed through the second integrator optical system 3 passes through a third lens 7 and a fourth lens 8, and then is emitted from the optical device 100. The laser light L emitted from the optical device 100 is irradiated onto an irradiation surface S. The irradiation surface S is, for example, a screen.

[0022] Here, laser light, which is a coherent light, is more susceptible to interference than incoherent light. Therefore, when the laser light is irradiated onto the irradiation surface S, the light scattered on the surface of the irradiation surface S may interfere with each other, causing speckle noise. When an image is displayed using the laser light emitted from an optical device, the occurrence of speckle noise causes uneven brightness and color, degrading the quality of the image.

[0023] The optical device 100 can emit two orthogonal polarized lights by rotating the polarized light of a portion of the laser light L emitted from the laser light source 1 by 90 degrees using the phase difference plate 4. Since the two orthogonal polarized lights do not interfere with each other, the optical device 100 can reduce speckle noise by emitting the two orthogonal polarized lights. In this specification, this is referred to as the "speckle noise reduction effect by polarization multiplexing."

[0024] In addition, the optical device 100 has two integrator optical systems including the first integrator optical system 2 and the second integrator optical system 3, and thus can increase the angle difference of the incidence angle of the laser light L emitted from the optical device 100 and onto the irradiation surface S. The angle difference of the light incidence angle onto the irradiation surface S means the angle difference between the incidence angle of one light and the incidence angle of the other light incident onto the irradiation surface S. The angle difference of the light incidence angle onto the irradiation surface S may be expressed in other words as the range of the light incidence angle onto the irradiation surface S. The larger the angle difference of the light incidence angle, the less likely the incident lights are to interfere with each other. The optical device 100 has two integrator optical systems including the first integrator optical system 2 and the second integrator optical system 3, and can reduce speckle noise by increasing the angle difference of the light incidence angle. In this specification, this is referred to as the "speckle noise reduction effect by angle multiplexing". The action of this angle multiplexing will be described separately with reference to FIG. 5.

[0025] In this embodiment, by using both polarization multiplexing and angle multiplexing, it is possible to provide the optical device 100 that can improve the speckle noise reduction performance. For example, by using both polarization multiplexing and angle multiplexing, the optical device 100 can improve the speckle noise reduction performance compared to the case where only polarization multiplexing is used.

[0026] In the optical device 100, the retardation plate 4 can transmit half of the laser light L emitted from the laser light source 1. For example, as shown in FIG. 2, the retardation plate 4 can be arranged so that half of the laser light L emitted from one of the semiconductor laser elements 11 passes through the retardation plate 4. In the example shown in FIG. 2, the retardation plate 4 is arranged to transmit half of each of the four laser lights L emitted from the four first semiconductor laser elements 11R, transmit half of each of the two laser lights L emitted from the two second semiconductor laser elements 11G, and transmit half of each of the two laser lights L emitted from the two third semiconductor laser elements 11B. With this arrangement, the laser light L emitted from each of the four first semiconductor laser elements 11R, two second semiconductor laser elements 11G, and two third semiconductor laser elements 11B can be split into two orthogonal polarized lights. By dividing the light into two orthogonal polarized lights, the effect of reducing speckle noise due to polarization multiplexing is nearly maximized, and speckle noise can be reduced compared to when polarization multiplexing is not used.

[0027] The laser light source 1 is a light emitting device having a plurality of semiconductor laser elements 11. Each of the semiconductor laser elements 11 emits laser light L. This allows the optical device 100 to emit brighter light than when light other than laser light is emitted and when laser light is emitted using one semiconductor laser element.

[0028] Furthermore, the laser light source 1 can emit a plurality of laser beams L having mutually different colors. This allows the optical device 100 to emit a mixed color light of the respective colors of the plurality of laser beams L.

[0029] The first integrator optical system 2 includes a first fly-eye lens 21 and a second fly-eye lens 22. Each of the first fly-eye lens 21 and the second fly-eye lens 22 is a plate-like member having a first surface 21a and a second surface 21b located on the opposite side to the first surface 21a. The first surface 21a and the second surface 21b are planes (e.g., XY planes) perpendicular to the optical axis A. The first surface 21a includes a plurality of first convex surfaces 210 arranged along the plane perpendicular to the optical axis A. The first fly-eye lens 21 and the second fly-eye lens 22 are disposed so that their second surfaces 21b face each other. From the viewpoint of productivity, the first fly-eye lens 21 and the second fly-eye lens 22 preferably have the same shape, but may have different shapes. In addition, the first fly-eye lens 21 and the second fly-eye lens 22 may be manufactured as an integrated member rather than as separate members.

[0030] In the example shown in FIG. 3, the shape of each of the multiple first convex surfaces 210 included in the first fly-eye lens 21 in a plan view is approximately hexagonal. The multiple first convex surfaces 210 are arranged with almost no gaps in a plan view. The shape of the first convex surface 210 in a plan view is not limited to an approximately hexagonal shape, and may be an approximately circular shape, an approximately elliptical shape, an approximately rectangular shape, an approximately polygonal shape other than a hexagon, or the like. The four first laser lights LR emitted from the four first semiconductor laser elements 11R, the two second laser lights LG emitted from the two second semiconductor laser elements 11G, and the two third laser lights LB emitted from the two third semiconductor laser elements 11B pass through the optical member 16 shown in FIG. 1 and are incident on the first fly-eye lens 21 as approximately parallel lights.

[0031] The second integrator optical system 3 is disposed at a position that is substantially conjugate with the first integrator optical system 2 by the first lens 5 and the second lens 6. The first illumination optical system 20 is configured such that the magnified conjugate images of the respective first convex surfaces 210 in the first integrator optical system 2 substantially overlap in the vicinity of the arrangement position of the second integrator optical system 3. As a result, in the vicinity of the arrangement position of the second integrator optical system 3, as shown in FIG. 4, the magnified conjugate images of the respective first convex surfaces 210 substantially overlap each other are obtained by the mixed color light Lm of the red laser light, the green laser light, and the blue laser light that have passed through the multiple first convex surfaces 210.

[0032] 4, the third fly-eye lens 31 is a plate-like member having a plurality of third convex surfaces 301 arranged along a plane perpendicular to the optical axis A. The plurality of third convex surfaces 301 are formed and connected as an integral member.

[0033] Each of the first integrator optical system 2, the second integrator optical system 3, the first lens 5, the second lens 6, the third lens 7, and the fourth lens 8 is made of a resin or glass having translucency to the laser light L emitted from the laser light source 1. Note that the translucency here preferably has a light transmittance of 60% or more to the laser light L.

[0034] 5, two orthogonal polarized lights, P polarized light Lp and S polarized light Ls, are irradiated onto the irradiation surface S through the second illumination optical system 30. The P polarized light Lp is the laser light L emitted from the laser light source 1 that has not been transmitted through the retardation plate 4. The S polarized light Ls is the laser light L emitted from the laser light source 1 that has been transmitted through the retardation plate 4.

[0035] As shown in FIG. 1, in the optical device 100, the retarder 4 can be disposed between the laser light source 1 and the first integrator optical system 2. With this arrangement, as shown in FIG. 5, the P polarized light Lp and the S polarized light Ls are incident on the irradiation surface S from directions that are substantially symmetrical with respect to the optical axis A, respectively. As a result, the angle difference between the incidence angle of the P polarized light Lp on the irradiation surface S and the angle difference between the incidence angle of the S polarized light Ls on the irradiation surface S are larger than when the P polarized light Lp and the S polarized light Ls are not incident on the irradiation surface S from directions that are symmetrical with respect to the optical axis A, respectively. As a result, in the optical device 100, the speckle noise reduction effect due to angle multiplexing can be increased compared to when the P polarized light Lp and the S polarized light Ls are not incident on the irradiation surface S from directions that are symmetrical with respect to the optical axis A, respectively.

[0036] In the optical device 100, the number and arrangement of the semiconductor laser elements 11 included in the laser light source 1 can be changed as appropriate. The configurations of the first illumination optical system 20 and the second illumination optical system 30 and the arrangements of the respective components can also be changed as appropriate. In addition, the laser light source 1 is not limited to one that emits a plurality of laser beams L having different colors, and may be one that emits a single-color laser beam L. In this case as well, the optical device 100 can reduce speckle noise.

[0037] <Another Example of the Positional Relationship Between the Laser Light Source 1 and the Retardation Plate 4> The positional relationship between the laser light source 1 and the retardation plate 4 can be modified in various ways in addition to the first example shown in Fig. 2. Here, other examples of the positional relationship between the laser light source 1 and the retardation plate 4 will be described. Note that the same names and symbols as those in the examples or embodiments already described indicate the same or similar members or configurations, and detailed descriptions will be omitted as appropriate. This also applies to the embodiments described below.

[0038] (Example 2) 6 is a schematic plan view showing a second example of the positional relationship between the laser light source 1 and the retardation plate 4 in the optical device 100. In the example shown in FIG. 6, the retardation plate 4 includes a first retardation plate 41 and a second retardation plate .

[0039] Each of the first retardation plate 41 and the second retardation plate 42 is, for example, a half-wave plate. Each of the first retardation plate 41 and the second retardation plate 42 is arranged such that the optical axis of the half-wave plate is inclined by 45 degrees with respect to the polarization direction of the linearly polarized light incident thereon. This allows the retardation plate 4 to rotate the polarization of the laser light transmitted through each of the first retardation plate 41 and the second retardation plate 42 by 90 degrees among the linearly polarized light incident thereon.

[0040] The first retardation plate 41 is arranged to transmit half of each of the four laser beams emitted from the four first semiconductor laser elements 11R. On the other hand, the second retardation plate 42 is arranged to transmit half of each of the two laser beams emitted from the two second semiconductor laser elements 11G, and transmit half of each of the two laser beams emitted from the two third semiconductor laser elements 11B. As a result, the retardation plate 4 can bisect the laser beams emitted from the four first semiconductor laser elements 11R, the two second semiconductor laser elements 11G, and the two third semiconductor laser elements 11B into two orthogonal polarized beams. By bisecting the laser beams into two orthogonal polarized beams, the effect of reducing speckle noise due to polarization multiplexing is almost maximized, and speckle noise can be reduced compared to when polarization multiplexing is not used.

[0041] [Second embodiment] An optical device according to the second embodiment will be described with reference to Fig. 7 and Fig. 8. Fig. 7 is a schematic cross-sectional view of an optical device 100a according to the second embodiment. Fig. 7 shows a cross-section of the optical device 100a cut along a virtual plane (e.g., YZ plane) including the optical axis A. Fig. 8 is a schematic cross-sectional view of the second illumination optical system 30 showing how two orthogonal polarized lights are incident on the irradiation surface S in the optical device 100a. Fig. 8 shows a cross-section of the second illumination optical system 30 cut along a virtual plane (e.g., YZ plane) including the optical axis A.

[0042] This embodiment differs from the first embodiment in that the retardation plate 4 is disposed between the first integrator optical system 2 and the second integrator optical system 3. In the example shown in Fig. 7 and Fig. 8, the retardation plate 4 is disposed in the vicinity of the arrangement position of the second integrator optical system 3 so as to transmit half of the mixed color light Lm obtained by the first illumination optical system 20.

[0043] 8, two orthogonal polarized lights, P polarized light Lp and S polarized light Ls, are irradiated onto the irradiation surface S through the second illumination optical system 30. The P polarized light Lp is the mixed color light Lm that has not passed through the retardation plate 4. The S polarized light Ls is the mixed color light Lm that has passed through the retardation plate 4.

[0044] In the optical device 100a, the retardation plate 4 is disposed between the first integrator optical system 2 and the second integrator optical system 3, so that the P polarized light Lp and the S polarized light Ls are incident on the irradiation surface S from directions that are substantially symmetrical with respect to the optical axis A, as shown in FIG. 8. That is, in the example shown in FIG. 8, most of the P polarized light Lp is irradiated onto the irradiation surface S through a space on the +Y side of the optical axis A, and most of the S polarized light Ls is irradiated onto the irradiation surface S through a space on the -Y side of the optical axis A. As a result, the angle difference between the angles of incidence of the P polarized light Lp on the irradiation surface S and the angle difference between the angles of incidence of the S polarized light Ls on the irradiation surface S become large. As a result, in the optical device 100a, the speckle noise reduction effect due to angle multiplexing can be increased.

[0045] In optical device 100a, the angle difference between the angles of incidence of P polarized light Lp onto irradiation surface S and the angle difference between the angles of incidence of S polarized light Ls onto irradiation surface S are each half compared to the first embodiment, where the P polarized light Lp and the S polarized light Ls are each incident on irradiation surface S from directions that are approximately symmetrical with respect to the optical axis A (see FIG. 5). Therefore, in optical device 100a, the effect of reducing speckle noise due to angle multiplexing is reduced compared to the first embodiment.

[0046] [Third embodiment] An optical device according to the third embodiment will be described with reference to Figs. 9 to 12. Fig. 9 is a schematic cross-sectional view showing a first example of the configuration of the periphery of the laser light source 1 in the optical device 100b according to the third embodiment. Fig. 10 is a schematic cross-sectional view showing a second example of the configuration of the periphery of the laser light source 1 in the optical device 100b. Figs. 9 and 10 each show a cross section of the periphery of the laser light source 1 of the optical device 100b cut by a virtual plane (e.g., a YZ plane) including the optical axis A. Note that the configuration of the optical device 100b other than the periphery of the laser light source 1 may be the same as that of the optical device 100 according to the first embodiment. Fig. 11 is a schematic plan view showing a first example of the positional relationship between the combined light Lu and the retardation plate 4 in the optical device 100b. Fig. 12 is a schematic plan view showing a second example of the positional relationship between the combined light Lu and the retardation plate 4 in the optical device b.

[0047] This embodiment further includes a combining optical system 14 that is disposed between the laser light source 1 and the first integrator optical system 2 and combines a plurality of laser beams L. The retardation plate 4 transmits a portion of the combined light Lu of the plurality of laser beams L by the combining optical system 14, thereby rotating the polarization of the transmitted combined light Lu by 90 degrees. These points are different from the first embodiment.

[0048] When the retardation plate 4 is arranged so as to transmit a part of each of the multiple laser beams, it is necessary to position the retardation plate 4 with high accuracy with respect to each of the multiple laser beams, and therefore it may take time to adjust the positioning. Furthermore, if the accuracy of the positioning adjustment is low, the speckle noise reduction effect may decrease. In this embodiment, by arranging the retardation plate 4 so as to transmit a part of the combined light Lu, it is possible to easily and accurately arrange the retardation plate 4 to reduce speckle noise, compared to the case where the retardation plate 4 is arranged so as to transmit a part of each of the multiple laser beams.

[0049] In a first example of the optical device 100b shown in FIG. 9 and a second example of the optical device 100b shown in FIG. 10, the laser light source 1 emits a plurality of laser lights L having different colors. The combining optical system 14 includes a mirror group 15 that combines the plurality of laser lights L having different colors. The combining optical system 14 also includes a beam expander 17 that expands the maximum width of the laser light L in a direction perpendicular to the optical axis A of the optical device 100b. In the first example shown in FIG. 9 and the second example shown in FIG. 10, the mirror group 15 is disposed between the laser light source 1 and the first integrator optical system 2. The beam expander 17 is disposed between the mirror group 15 and the first integrator optical system 2.

[0050] In the first example shown in FIG. 9 and the second example shown in FIG. 10, the mirror group 15 includes a mirror 151, a first dichroic mirror 152, and a second dichroic mirror 153. The mirror 151 reflects the first laser light LR emitted from the first semiconductor laser element 11R toward the beam expander 17. The first dichroic mirror 152 reflects the second laser light LG emitted from the second semiconductor laser element 11G toward the beam expander 17, and transmits the first laser light LR reflected by the mirror 151. The second dichroic mirror 153 reflects the third laser light LB emitted from the third semiconductor laser element 11B toward the beam expander 17, and transmits each of the first laser light LR reflected by the mirror 151 and the second laser light LG reflected by the first dichroic mirror 152. The mirror 151 may be a dichroic mirror.

[0051] The first laser light LR, the second laser light LG, and the third laser light LB are combined by the mirror group 15 to become a combined light Lu. The combined light Lu is a light that is approximately parallel to the optical axis A and is a mixture of red, green, and blue. The combined light Lu is incident on the beam expander 17. Note that the mirror group 15 is not limited to one that includes the mirror 151, the first dichroic mirror 152, and the second dichroic mirror 153, as long as it can combine a plurality of laser lights L that are different from each other in color. For example, the number and arrangement of the mirrors and dichroic mirrors may be appropriately changed according to the number and arrangement of the semiconductor laser elements 11 included in the laser light source 1.

[0052] The beam expander 17 includes a concave lens 171 and a convex lens 172. The beam expander 17 expands the maximum width of the combined light Lu from the mirror group 15 in a direction perpendicular to the optical axis A. The combined light Lu whose maximum width has been expanded by the beam expander 17 is also light substantially parallel to the optical axis A. The width W in each of the first example shown in FIG. 9 and the second example shown in FIG. 10 represents the maximum width of the combined light Lu after being expanded by the beam expander 17. Note that the beam expander 17 is not limited to one including the concave lens 171 and the convex lens 172, as long as it can expand the maximum width of the incident light in a direction perpendicular to the optical axis A. For example, it may be a configuration including two or more convex lenses.

[0053] The combining optical system 14 includes the mirror group 15, and can combine a plurality of laser lights L of different colors emitted from the laser light source 1. This allows the retardation plate 4 to be arranged easily and with high accuracy to reduce speckle noise even when a plurality of laser lights L of different colors are used. In addition, the combining optical system 14 includes the beam expander 17, and can obtain a combined light Lu whose maximum width in a direction perpendicular to the optical axis A is expanded. Compared to a case where the beam expander 17 is not included, the retardation plate 4 to reduce speckle noise can be arranged more easily and with high accuracy. The combining optical system 14 does not necessarily include both the mirror group 15 and the beam expander 17, and may include at least one of the mirror group 15 and the beam expander 17.

[0054] In a first example shown in FIG. 9, the retardation plate 4 is disposed between the combining optical system 14 and the first integrator optical system 2. The combined light Lu by the combining optical system 14 is perpendicularly incident on the incident surface 40 of the retardation plate 4. As shown in FIG. 11 and FIG. 12, the retardation plate 4 can transmit a part of the combined light Lu by the combining optical system 14. In the example shown in FIG. 11, the shape of the retardation plate 4 in a plan view is a substantially rectangular shape with the vertical direction (e.g., Y direction) as the long side, and can transmit half of the combined light Lu by the combining optical system 14 in the horizontal direction (e.g., X direction). On the other hand, in the example shown in FIG. 12, the shape of the retardation plate 4 in a plan view is a substantially rectangular shape with the horizontal direction as the long side, and can transmit half of the combined light Lu by the combining optical system 14 in the vertical direction.

[0055] 9, the combined light Lu from the combining optical system 14 is perpendicularly incident on the incident surface 40 of the retardation plate 4, so that the retardation plate 4 can provide a phase difference of 1 / 2 wavelength to the combined light Lu with high precision. As a result, the retardation plate 4 can rotate the polarization direction of the transmitted combined light Lu by 90 degrees with high precision, so that the optical device 100b can increase the effect of reducing speckle noise.

[0056] 10, the retardation plate 4 is disposed on the opposite side (e.g., +Z side) of the first integrator optical system 2 from the side (e.g., -Z side) where the combining optical system 14 is located. For example, when the retardation plate 4 is disposed between the combining optical system 14 and the first integrator optical system 2, the combined light Lu, which is substantially parallel light, is incident on the retardation plate 4, and thus the amount of scattered light of the combined light Lu may increase at the end of the retardation plate 4, for example, at the end on the -Y side. When the scattered light is superimposed on the laser light Lu emitted from the optical device 100b, the quality of the laser light Lu emitted from the optical device 100b decreases.

[0057] 10, by arranging the retarder 4 on the side of the first integrator optical system 2 opposite to the side where the combining optical system 14 is located, it is possible to reduce scattering of the combined light Lu at the end of the retarder 4 compared to the case where the retarder 4 is arranged between the combining optical system 14 and the first integrator optical system 2. This reduces scattered light superimposed on the laser light Lu emitted from the optical device 100b, and improves the quality of the laser light Lu emitted from the optical device 100b. The other effects of the optical device 100b according to the second example are similar to those of the optical device 100b according to the first example.

[0058] [Fourth embodiment] Fig. 13 is a schematic cross-sectional view of an optical device 100c according to a fourth embodiment. Fig. 13 shows a cross section of the optical device 100c cut along a virtual plane including the optical axis A (for example, a YZ plane).

[0059] This embodiment differs from the first embodiment in that an optical device 100c has a second integrator optical system 3c that includes a light pipe.

[0060] In the example shown in Fig. 13, the optical device 100c has a second integrator optical system 3c including a light pipe, and a fifth lens 9. The light pipe is, for example, a rod lens or a hollow light pipe. The second integrator optical system 3c and the fifth lens 9 configure a second illumination optical system 30c. The laser light L emitted from the laser light source 1 and passing through the first illumination optical system 20 passes through the second illumination optical system 30c and is irradiated onto the illumination surface S.

[0061] In the optical device 100c, a portion of the laser light is transmitted through a phase difference plate 4 arranged between the laser light source 1 and the second integrator optical system 3c, and the polarization of the transmitted laser light L is rotated by 90 degrees, thereby achieving the speckle noise reduction effect due to polarization multiplexing.

[0062] [Fifth embodiment] Fig. 14 is a schematic cross-sectional view of a display device 200 according to a fifth embodiment. Fig. 14 shows a cross section of the display device 200 cut along a virtual plane (for example, a YZ plane) including the optical axis A of the optical device 100.

[0063] This embodiment differs from the first embodiment in that the display device 200 includes an optical device 100, a spatial modulator 201 that generates an image by modulating the spatial intensity distribution of laser light L from the optical device 100, and a lens 202 that projects the image generated by the spatial modulator 201.

[0064] The spatial modulator 201 includes an LCD (Liquid Crystal Display), a DMD (Digital Micromirror Device), or the like. The display device 200 is, for example, a projector. The display device 200 can display an image on a projection surface such as a screen by projecting an image generated by the spatial modulator 201 onto the projection surface using a lens 202.

[0065] The laser light L emitted from the optical device 100 to the spatial modulator 201 is polarization-multiplexed and angle-multiplexed to reduce the occurrence of speckle noise. Therefore, the display device 200 can project an image with reduced speckle noise onto the projection surface, and display a high-quality image with reduced luminance and color unevenness resulting from speckle noise on the projection surface.

[0066] The optical device included in the display device 200 is not limited to the optical device 100, but may be any one of the optical device 100a, the optical device 100b, and the optical device 100c.

[0067] Although the preferred embodiments have been described in detail above, the present invention is not limited to the above-described embodiments, and various modifications and substitutions can be made to the above-described embodiments without departing from the scope of the claims.

[0068] The ordinal numbers, quantities, and other numbers used in the description of the embodiments are all provided as examples to specifically explain the technology of the present disclosure, and the present disclosure is not limited to the illustrated numbers. Furthermore, the connection relationships between the components are provided as examples to specifically explain the technology of the present disclosure, and do not limit the connection relationships that realize the functions of the present disclosure.

[0069] The optical device of the present disclosure can be suitably used as a light source device in various devices, apparatuses, or systems using laser light, since the speckle noise reduction performance can be improved. For example, the optical device of the present disclosure can be suitably used as a light source device in a display device such as a projector or a head-up display, or a head-mounted display device such as a head-mounted display. The optical device of the present disclosure can also be used as a light source device in lighting equipment, lighting systems such as smart lighting and energy-saving lighting, drawing devices mounted on vehicles or aircraft, spatial three-dimensional drawing devices, underwater drawing systems, etc.

[0070] Aspects of the present disclosure are, for example, as follows. <Item 1> An optical device comprising: a laser light source; a first integrator optical system that transmits laser light emitted from the laser light source; a second integrator optical system that transmits the laser light emitted from the first integrator optical system; and a retardation plate that is disposed between the laser light source and the second integrator optical system and transmits a portion of the laser light, thereby rotating polarization of the transmitted laser light by 90 degrees. <Item 2> The optical device according to <Item 1>, wherein the retardation plate transmits half of the laser light. <Item 3> The optical device according to <Item 1> or <Item 2>, wherein the laser light source is a light emitting device having a plurality of semiconductor laser elements, each of the semiconductor laser elements emitting the laser light. <Item 4> In the optical device according to <Item 3>, the phase difference plate is disposed so that half of the laser light emitted from one of the semiconductor laser elements passes through the phase difference plate. <Item 5> The optical device according to any one of <Item 1> to <Item 4>, wherein the laser light source emits a plurality of laser beams having mutually different colors. <Item 6> The optical device according to any one of <Item 1> to <Item 5>, wherein the retardation plate is disposed between the laser light source and the first integrator optical system. <Item 7> The optical device according to any one of <Item 1> to <Item 6>, wherein the retardation plate is disposed between the first integrator optical system and the second integrator optical system. <Item 8> The optical device according to any one of <Item 1> to <Item 7>, further comprising a combining optical system disposed between the laser light source and the first integrator optical system and combining a plurality of the laser beams, wherein the retardation plate transmits a portion of the combined light of the plurality of the laser beams by the combining optical system, thereby rotating the polarization of the transmitted combined light by 90 degrees. <Item 9> The optical device described in <Item 8>, wherein the laser light source emits a plurality of laser beams having mutually different colors, and the combining optical system includes a group of mirrors that combines the plurality of laser beams having mutually different colors. <Item 10> The optical device according to <Item 8> or <Item 9>, wherein the combining optical system includes a beam expander that expands a maximum width of the laser light in a direction perpendicular to an optical axis of the optical device. <Item 11> The optical device according to any one of <Item 8> to <Item 10>, wherein the retardation plate is disposed between the combining optical system and the first integrator optical system, and the combined light by the combining optical system is incident perpendicularly to an incident surface of the retardation plate. <Item 12> The optical device according to any one of <Item 8> to <Item 11>, wherein the retardation plate is disposed on the side of the first integrator optical system opposite to the side on which the combining optical system is located. <Item 13> A display device comprising: an optical device according to any one of <Item 1> to <Item 12>; a spatial modulator that generates an image by modulating the spatial intensity distribution of the laser light from the optical device; and a lens that projects the image generated by the spatial modulator. [Explanation of symbols]

[0071] 1 Laser light source 11 Semiconductor laser element 11R First semiconductor laser element 11G Second semiconductor laser element 11B Third semiconductor laser element 12 Lid member 13 Substrate 14 Synthetic optical system 15 Mirror Group 16 Optical components 151 Mirror 152 1st dichroic mirror 153 2nd Dichroic Mirror 17 Beam Expander 171 Concave Lens 172 Convex Lens 2 First integrator optical system 21 First fly-eye lens 21a 1st page 21b 2nd side 210 1st convex surface 22 2nd fly-eye lens 3, 3c Second integrator optical system 31 3rd fly-eye lens 4 Retardation plate 40 Entrance plane 41 1st retardation plate 42 Second retardation plate 5 First lens 6 Second lens 7 Third lens 8 Fourth lens 9 Fifth lens 20 1st illumination optical system 30, 30c 2nd illumination optical system 100, 100a, 100b, 100c optical equipment 200 Display device 201 Spatial Modulator 202 Lens A optical axis L Laser light Lm mixed color light LR 1st laser beam LG 2nd laser light LB 3rd laser beam Lp P polarized light Ls S polarized light Lu synthetic light S Irradiation surface W width

Claims

1. A laser light source; a first integrator optical system that transmits the laser light emitted from the laser light source; a second integrator optical system that transmits the laser light emitted from the first integrator optical system; a retardation plate disposed between the laser light source and the second integrator optical system, the retardation plate transmitting a portion of the laser light and thereby rotating the polarization of the transmitted laser light by 90 degrees.

2. The optical device of claim 1 , wherein the retardation plate transmits half of the laser light.

3. the laser light source is a light-emitting device having a plurality of semiconductor laser elements, The optical device according to claim 1 , wherein each of the semiconductor laser elements emits the laser light.

4. 4. The optical device according to claim 3, wherein the retardation plate is disposed so that half of the laser light emitted from one of the semiconductor laser elements passes through the retardation plate.

5. The optical device according to claim 1 , wherein the laser light source emits a plurality of laser beams having mutually different colors.

6. The optical device according to claim 1 , wherein the retardation plate is disposed between the laser light source and the first integrator optical system.

7. The optical device according to claim 1 , wherein the retardation plate is disposed between the first integrator optical system and the second integrator optical system.

8. a combining optical system disposed between the laser light source and the first integrator optical system, the combining optical system combining a plurality of the laser beams; The optical device according to claim 1 , wherein the phase difference plate transmits a portion of the combined light of the plurality of laser beams produced by the combining optical system, thereby rotating the polarization of the transmitted combined light by 90 degrees.

9. The laser light source emits a plurality of laser beams having different colors, The optical device according to claim 8 , wherein the combining optical system includes a group of mirrors that combines the plurality of laser beams having mutually different colors.

10. The optical device according to claim 8 , wherein the combining optical system includes a beam expander that expands a maximum width of the laser light in a direction perpendicular to an optical axis of the optical device.

11. the retardation plate is disposed between the combining optical system and the first integrator optical system, The optical device according to claim 8 , wherein the combined light from the combining optical system is incident perpendicularly to an incident surface of the retardation plate.

12. The optical device according to claim 8 , wherein the retardation plate is disposed on a side of the first integrator optical system opposite to a side on which the combining optical system is located.

13. An optical device according to any one of claims 1 to 12; a spatial modulator that generates an image by modulating a spatial intensity distribution of the laser light from the optical device; and a lens for projecting the image generated by the spatial modulator.

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